What is Line of Sight behavior?

A built-in behavior in Construct 3 that checks if a clear line exists between an object and a target, with configurable obstacles. Used for AI vision cones, lasers, etc.

Why does LoS fail when target is the same family?

If you mark EnemyFamily as an obstacle (for ‘enemies block sight’), the source enemy itself counts. The LoS ray starts inside its own collision box and immediately reports blocked.

How do I exclude self?

Temporarily set the source instance’s collision to disabled before checking, or move the LoS origin slightly outward. Behavior’s built-in obstacle list doesn’t support per-instance exclude directly.

Fix: Construct 3 Line Of Sight Blocked By Self

Quick answer: Disable the source enemy’s collisions just for the LoS check (then re-enable), or set the obstacle list to specific obstacle objects (walls only), not the EnemyFamily.

A stealth game uses Line of Sight to let enemies spot the player. EnemyFamily is in the LoS “blocks sight” obstacle list (because enemies block each other). LoS always returns false even with clear path. Source enemy blocks itself.

Cause

The LoS ray starts inside the source enemy’s collision box. Since the family is an obstacle, the ray immediately hits and reports blocked.

Fix 1: Temporarily Disable Collisions

For each EnemyFamily
    EnemyFamily → Set collisions Disabled
    EnemyFamily has LoS to Player
        → RaiseAlarm
    EnemyFamily → Set collisions Enabled

Disable for the check, re-enable immediately. Cheap, reliable. Works because the LoS check is synchronous within the same tick.

Fix 2: Restrict Obstacle List

If “enemies block each other’s sight” isn’t critical to gameplay, simplify:

Set LoS “Obstacles” to Solid behavior or a Wall family only.
Enemies still avoid each other for collision but don’t block sight.

Simpler, no per-tick toggling.

Fix 3: Offset LoS Origin

Position the LoS check from a slightly-outside point:

System → Pick by comparison: distance(EnemyFamily.X+8*cos(EnemyFamily.angle), ..., Player.X, ...) < sight_range

Hacky; the “disable collision” approach is cleaner.

Verifying

With several enemies and a player: each enemy in line of sight reports true. Walls block. Enemies in the way of another enemy’s LoS block according to your chosen rule.

“Self-collision is a perennial issue for vision rays. Disable-then-restore is the standard fix.”

For stealth games, an enemy not blocking another’s sight feels okay — players don’t notice. Simplify and ship.